The invention relates to fluid delivery applications and more specifically to a system for achieving a controlled low emission rate for small volumes of chemical agents for pest and insect management. The emission of chemical agents such as insecticides, pesticides, pheromones, etc. to control pests, frequently requires controlled and accurate rates of delivery, if specific results, such as kill rate, mating interruption, aggregation prevention, etc., have to be achieved, effectively. Whenever multi-component chemical agent blends are required, it is extremely difficult to achieve and maintain the desired emission rates, using existing delivery devices, or emitters.
The examples recited below from published experiments, illustrate the need for release control and show that available devices do not satisfy this need.
In Japan, the tea tortrix is a serious pest, on tea plants. Pest control can be achieved by mating disruption, using Z-11-TDA (Z-11 tetradecenylacetate) as the mating interruption pheromone. In these experiments, it was possible to show the following agent activity.
Mating disruption is proportional to pheromone release rate. Therefore, the emitter, preset for a specific rate, should sustain it, since mating is not appreciably prevented below rates of 2000 mg/day/ha. Furthermore, since different dose rates are needed in different areas, the emitter should be flexible enough to accommodate different rates.
In another controlled test, small moths (Prays oleae), lured by PBX, were trapped in five successive time periods by four different doses, ranging from 0.1 to 20.0 mg. The dose-response relationship, reported below, points to a maximum catch, at 1.0 mg, which is twice that for any other doses.
Obviously, the effectiveness of the trap is strongly affected by the ability to maintain a 1.0 mg dose.
In Western Europe, four species of tortridid moths infest fruit orchards. All species use dodec-8-en-1-o1 acetate (8-12-26 Ac) as major component, available as (Z) or (E) isomers. However, 100% attractivity towards the binary mixture is achieved in the following manner:
In this case, the integrity of the species is maintained by differentiating blend compositions. Therefore, if both isomers are not emitted at the appropriate rate, multiple species may be attracted.
In British Columbia (1991), verbenone was tested as an anti-aggregation pheromone for mountain pine beetle. At an emission rate of 3.8 mg/day, from a concentrated source, the pheromone completely inhibited response to an attractant blend consisting of myrcene, exo-brevicomin and trans-verbenol. When verbenone was released from beads on the forest floor, effectiveness was reduced by 50%. When exposed to sunlight, 50% of verbenone was converted to the inactive chrysanthenone, within 75 to 100 minutes. Rapid isomerization probably reduced verbenone concentration to below biologically active levels. This illustration points to the specific need of point sources and to the danger of exposing the pheromone to sunlight.
Similarly, in another antiaggregation experiment, an optimum dosage of verbenone was determined to reduce infestation of mountain pine beetle in lodgepole pines in Central Idaho.
The results of the previous experiments are used as a way to illustrate the critical nature of pheromone concentration, the narrow concentration ranges for effectiveness, the need to emit from concentrated, or point, sources, and the specificity of the emission rate. Point sources are only symptomatic of the need to create a repeatable concentration gradient to which the insects are responding.
Pheromone dispensers can be grouped in two general classes: passive devices, which are based on natural forces (evaporation, diffusion, etc.) and active devices which require man-made energy sources (batteries, springs, etc.)
Passive Devices
Plastic Laminate Dispensers contain pheromone trapped between layers of plastic films. The emission rate is proportional to the inverse of square root of time, such that Rate=a txe2x88x92xc2xd where (a) is a characteristic of film properties and geometry. Devices of this type display a high initial emission rate progressively decreasing to zero. This behavior is characteristic of first order kinetics, i.e. the rate is concentration-dependent. Since the coefficient (a) is also dependent on the properties of the pheromone, it is 1) difficult to control the rate, and 2) in the case of multicomponent blends it is not possible to control the concentration ratios of individual components. Hollow fibers are used as capillaries from which the pheromone diffuses through the vapor-air volume, considered the rate-controlling step. Therefore, the rate should be predictable. However, liquid retention within walls and fiber cross-channels result in a release rate between order zero and one commercial success is further hampered by the financial investment in the equipment required to process the fiber bundles.
Microcapsules consist of packaging chemicals in a microgranular form with stabilizing agents. The 1-1000 microns diameter capsule contains the pheromone which is therefore protected from the environment, i.e. light and oxygen. Again, since the active ingredient concentration within the capsule changes with time, the emission rate is first order, i.e. time-dependent.
Other dispensers have also been developed and used. They include polyethylene tubes, rubber septa, polyvinyl chloride rods or pellets, cigarette filters, polyethylene vial caps, dental roll, etc.
In summary, none of the existing and currently-in-use dispensers can achieve the xe2x80x9cidealxe2x80x9d zero-order delivery, or the sustained release of multiple pheromones at concentration ratios required for an effective use of generally expensive chemical agents.
It will be the primary object of the present invention to show that xe2x80x9cidealxe2x80x9d control release is achievable.
Active Devices
Timed release spray dispensers have been used for mating interruption of the blackheaded fireworm. A battery-powered timing mechanism operating a valve is used to spray the sex pheromone solution at preset time intervals. Spray dispensers are nearly zero-order release devices. However, the intermittent delivery results in xe2x80x9cspurtxe2x80x9d emission, thereby creating a discontinuous release.
The object of this invention will be to demonstrate xe2x80x9ccontinuousxe2x80x9d emission.
Although the previous examples specifically describe pheromones, the present invention is also suitable for liquids such as fragrances, insect formulations, sanitizers, disinfectants, repellents, aromatherapuetic formulations, or any other such liquid requiring delivery in a controlled manner.
The following summarizes certain desired dispenser features and attributes and emitter characteristics, albeit not necessarily achievable simultaneously.
Compatibility with most pheromones
Compatibility with a variety of solvents, diluents, additives, ranging from water to functional chemicals to hydrocarbons
Compatible with multicomponent blends
Maintaining the relative concentration ratios of all components in solution
Long term (6 months) storage of the pheromone in the dispenser without adverse effects (evaporation, phase separation, chemical changes, etc.)
Protection from light, UV and oxygen
Release at xe2x80x9cquasixe2x80x9d steady state (zero-order)
Release of multicomponent blends without affecting individual component rates
Readily changeable delivery rate, i.e. use of the dispenser for a variety of different rates, with minor changes.
Long term delivery capability
Ease of filling and sealing the reservoir
Ease of start-up
Small investment in filing/sealing equipment
Ease of field placement
Economical
The object of the present invention is to satisfy most, or all, of the desirable features of dispensers described above, with emphasis on constant release rate for long time periods and the maintenance of the desired concentration ratios throughout release.
Constant release rates of fluids can be achieved by using pumps. However, since pheromone delivery rates are of the order of 5 to 50,000 micrograms/hour (5 nanoliter to 50 microliters/hour) no practical economical delivery devices are available at the nanoliter/hour rate although they are available at the microliter/hour rate. Therefore, by selecting appropriate solvents, it is possible to increase the release rate to the practical microliter/hour level.
Since emanation of pheromone has to be performed over long time periods, i.e. 100 days or more (2400 hours) the total fluid volume should be maintained within manageable limits, i.e. 5 to 25 mL.
A suitable fluid delivery pump with pre-set or programmable flow rates to achieve a time-dependent fluid delivery profile, which includes a power source that can be a battery or wall power, a pumping mechanism and fluid reservoir, has already been described in previous patents, namely Maget et al in U.S. Pat. No. 4,902,278; Maget in U.S. Pat. No. 5,928,194 where examples of devices operating at rates of 3.3 to 4.4 microliters/hour are reported, expelling liquid from the reservoir to a matrix material, and in U.S. Pat. No. 5,938,640 (Maget et al) which describes a fluid dispenser with a re-usable pumping module and disposable reservoir.
Electrochemical pumps, of the type described in U.S. Pat. No. 4,902,278 have been operated xe2x80x9coutdoorsxe2x80x9d for periods to 35 days, maintaining a constant flow rate of 11.1 microliters/hour, while dispensing a multicomponent fluid consisting of a diluent (ethylene glycol) and a ternary pheromone mixture consisting of verbenone, ipsdienol and methylcyclohexenone.
Electrochemical pumps can operate with a variety of fluids, including many solvents such as ethanol, water, heptane, ethylene glycol, butanediol.
The next step following controlled release of the fluid is the capture, dispersion and retention of the solvent/pheromone mixture by a collector from which solvent and pheromone can evaporate and emanate.
Suitable fluid collectors are absorbent pads located adjacent to the fluid release channel, which receive the mixture, disperse it by wetting the pad, and from which solvent and pheromone can evaporate, albeit at different rates.
For example, if the solvent is heptane, the evaporation rate is substantial and dispersion is minimal. If the diluent is ethylene glycol, the evaporation rate is low and considerable invasion of the pad will take place.
Emanation of the pheromone is the subsequent step. Although pheromone vapor pressures can be rather low (less than 0.5 mm Hg for a solid such as verbenol) the evaporation surface can be substantial and therefore the pheromone emanates nearly instantaneously without accumulation on the pad.
In most instances, the emanation rate of the pheromones exceeds the fluid delivery rate (and therefore the emanation rate is identical to the fluid delivery rate), thus achieving a zero-order emission.
Additivexe2x80x94a substance added to another in relatively small amounts to impart or improve desirable properties or suppress undesirable properties (such as a stabilizer to prevent the action of light or an antioxidant to prevent degradation by oxygen).
Aromatherapyxe2x80x94a treatment involving fragrants or strong scents.
Chemical agent (s)xe2x80x94a natural or synthetic compound or blend formulated for a specific action.
Diluentxe2x80x94an agent that makes thinner or less concentrated by admixture.
Dispenserxe2x80x94a device releasing material (gas, liquid or solid).
Electrochemical pumpxe2x80x94a pumping device based on the use of an electrochemical process: electrolysis, oxygen enrichment from air, galvanic reaction, resulting in gas generation.
Electromechanical pumpxe2x80x94an electrically or electronically controlled pump.
Emanatexe2x80x94to come from a source.
Emissionxe2x80x94the act of discharging (into the air).
Emitterxe2x80x94a device that sends out.
First-orderxe2x80x94a reaction or process which decreases progressively with time.
Fragrancexe2x80x94a sweet or delicate odor.
Gas pumpxe2x80x94a pumping device based on the use of gases generated through chemical reaction, or stored gas (carbon dioxide generator-based pump, Freon pump, carbon dioxide stored pump).
Mechanical pumpxe2x80x94a pumping device using mechanical stored energy such as a spring.
Pesticide, Insecticidesxe2x80x94an agent that destroys pests or insects.
Pumpxe2x80x94device used to transfer a liquid from one location to another.
Pheromonexe2x80x94a chemical released by an animal for a specific purpose.
Semiochemicalxe2x80x94chemical involved in communication by insects.
Solventxe2x80x94chemical capable of dissolving or dispersing one or more chemicals.
Zero-orderxe2x80x94a reaction or process which is constant with time.